US20210225860A1 - Semiconductor storage device - Google Patents
Semiconductor storage device Download PDFInfo
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- US20210225860A1 US20210225860A1 US17/010,190 US202017010190A US2021225860A1 US 20210225860 A1 US20210225860 A1 US 20210225860A1 US 202017010190 A US202017010190 A US 202017010190A US 2021225860 A1 US2021225860 A1 US 2021225860A1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B43/00—EEPROM devices comprising charge-trapping gate insulators
- H10B43/10—EEPROM devices comprising charge-trapping gate insulators characterised by the top-view layout
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- H01L27/11575—
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/481—Internal lead connections, e.g. via connections, feedthrough structures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
- H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
- H01L23/5226—Via connections in a multilevel interconnection structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
- H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
- H01L23/528—Geometry or layout of the interconnection structure
- H01L23/5283—Cross-sectional geometry
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
- H01L23/535—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including internal interconnections, e.g. cross-under constructions
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- H01L27/11565—
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- H01L27/1157—
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- H01L27/11573—
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- H01L27/11582—
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B43/00—EEPROM devices comprising charge-trapping gate insulators
- H10B43/20—EEPROM devices comprising charge-trapping gate insulators characterised by three-dimensional arrangements, e.g. with cells on different height levels
- H10B43/23—EEPROM devices comprising charge-trapping gate insulators characterised by three-dimensional arrangements, e.g. with cells on different height levels with source and drain on different levels, e.g. with sloping channels
- H10B43/27—EEPROM devices comprising charge-trapping gate insulators characterised by three-dimensional arrangements, e.g. with cells on different height levels with source and drain on different levels, e.g. with sloping channels the channels comprising vertical portions, e.g. U-shaped channels
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B43/00—EEPROM devices comprising charge-trapping gate insulators
- H10B43/30—EEPROM devices comprising charge-trapping gate insulators characterised by the memory core region
- H10B43/35—EEPROM devices comprising charge-trapping gate insulators characterised by the memory core region with cell select transistors, e.g. NAND
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B43/00—EEPROM devices comprising charge-trapping gate insulators
- H10B43/50—EEPROM devices comprising charge-trapping gate insulators characterised by the boundary region between the core and peripheral circuit regions
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B43/00—EEPROM devices comprising charge-trapping gate insulators
- H10B43/40—EEPROM devices comprising charge-trapping gate insulators characterised by the peripheral circuit region
Definitions
- Embodiments described herein relate generally to a semiconductor storage device.
- a semiconductor storage device including a three-dimensional memory cell array is developed. Memory cells of such a semiconductor storage device are three-dimensionally arranged.
- a local wiring that connects a source layer provided below the memory cell array to an upper wiring is provided in a tap area between the adjacent memory cell arrays.
- the local wiring is formed by embedding a low resistance metal such as tungsten in a groove (a slit) in the tap area to prevent warpage of a substrate and to allow formation concurrently with contacts.
- a current from the source layer flows from the local wiring to the upper wiring via a via contact.
- the current concentrates on the via contact between the local wiring and the upper wiring, which may melt the via contact.
- FIG. 1 is a perspective view illustrating an example of a configuration of a semiconductor storage device.
- FIG. 2 is a cross-sectional view illustrating an example of a configuration of a columnar portion.
- FIG. 3 is a plan view illustrating an example of the configuration of the columnar portion.
- FIG. 4 is a plan view illustrating an example of the configuration of the semiconductor storage device according to the embodiment.
- FIG. 5 is a plan view illustrating a memory cell array of a frame B 1 in FIG. 4 in more detail.
- FIG. 6 is a plan view illustrating a tap area of a frame B 2 in FIG. 5 in more detail.
- FIG. 7 is a plan view illustrating a part of a memory cell array of a frame B 3 in FIG. 6 in more detail.
- FIG. 8 is a plan view illustrating a connection relationship between the columnar portion and a bit line.
- FIG. 9 is a cross-sectional view taken along a line 9 - 9 in FIG. 7 .
- FIG. 10 is a cross-sectional view taken along a line 10 - 10 in FIG. 7 .
- FIG. 11 is a plan view illustrating a part of a tap area of a frame B 4 in FIG. 6 in more detail.
- FIG. 12 is a cross-sectional view taken along a line 12 - 12 in FIG. 11 .
- FIG. 13 is a cross-sectional view taken along a line 13 - 13 in FIG. 11 .
- FIG. 14 is a cross-sectional view taken along a line 14 - 14 in FIG. 11 .
- FIG. 15 is a plan view illustrating an example of a configuration of a semiconductor storage device according to a first modification.
- FIG. 16 is a plan view illustrating an example of a configuration of a semiconductor storage device according to a second modification.
- Embodiments provide a semiconductor storage device capable of preventing melting of a via contact between a local wiring connected to a source layer and an upper wiring thereabove.
- a semiconductor storage device includes: a memory cell array including a stacked body having a plurality of insulating layers and a plurality of conductive layers are alternately stacked, wherein the memory cell array includes a cell area that includes a plurality of memory cells and a contact area provided adjacent the cell area; a circuit provided below the memory cell array; a source layer provided between the memory cell array and the circuit; a first contact provided in the contact area, and coupled to the circuit by extending along a stacking direction of the stacked body; a second contact provided over the cell area and the contact area, and coupled to the source layer by extending along the stacking direction; a first wiring extending in a direction intersecting an extending direction of the second contact in the contact area; a second wiring provided above the second contact, extending along the second contact in the contact area, and connected to the first wiring; and a plurality of third contacts provided between the second wiring and the second contact.
- a vertical direction of a semiconductor substrate indicates a relative direction when a surface on which a semiconductor element is provided is defined as UP, and may be different from a vertical direction according to acceleration of gravity.
- the drawings are schematic or conceptual, and a proportion of each portion is not necessarily the same as that of the actual one.
- the same elements as those described above with reference to the already illustrated drawings will be denoted by the same reference signs, and detailed description thereof will be appropriately omitted.
- FIG. 1 is a perspective view illustrating an example of a configuration of a semiconductor storage device.
- a semiconductor storage device 100 may be, for example, a NAND type flash memory including a three-dimensional memory cell array MCA in which memory cells are three-dimensionally arranged.
- a stacking direction of a stacked body 2 is defined as a Z direction.
- a direction that intersects the Z direction (for example, that is orthogonal the Z direction) is defined as a Y direction.
- a direction that intersects each of the Z and Y directions (for example, that is orthogonal to each of the Z and Y directions) is defined as an X direction.
- the semiconductor storage device 100 includes abase body portion 1 , the stacked body 2 , and a plurality of columnar portions CL.
- the base body portion 1 includes a substrate 10 , an insulating film 11 , a conductive film 12 , and a semiconductor layer 13 .
- the insulating film 11 is provided on the substrate 10 .
- the conductive film 12 is provided on the insulating film 11 .
- the semiconductor layer 13 is provided on the conductive film 12 .
- the substrate 10 is a semiconductor substrate, for example, a p-type silicon substrate.
- an element isolation area 10 i is provided in a front surface area of the substrate 10 .
- the element isolation area 10 i is, for example, an insulating area containing a silicon oxide, and partitions an active area AA in the front surface area of the substrate 10 .
- a source area and a drain area of a transistor Tr are provided in the active area AA.
- the transistor Tr forms a peripheral circuit (for example, a complementary metal oxide semiconductor (CMOS) circuit) of the nonvolatile memory.
- the insulating film 11 contains, for example, silicon oxide (SiO 2 ), and insulates the transistor Tr.
- a wiring 11 a is provided in the insulating film 11 .
- the wiring 11 a is a wiring electrically connected to the transistor Tr.
- the conductive film 12 contains a conductive metal such as tungsten (W).
- the semiconductor layer 13 contains, for example, silicon.
- a conductivity type of silicon is, for example, an n-type.
- a part of the semiconductor layer 13 may contain undoped silicon.
- the stacked body 2 is located in the Z direction with respect to the semiconductor layer 13 .
- the stacked body 2 is configured such that a plurality of conductive layers 21 and a plurality of insulating layers 22 are alternately stacked along the Z direction.
- the conductive layer 21 contains a conductive metal, such as tungsten.
- the insulating layer 22 contains a silicon oxide.
- the insulating layer 22 insulates the conductive layers 21 from each other. The number of layers of each of the conductive layer 21 and the insulating layer 22 is freely selected.
- the insulating layer 22 may be, for example, an air gap.
- an insulating film 2 g is provided between the stacked body 2 and the semiconductor layer 13 .
- the insulating film 2 g contains, for example, a silicon oxide (SiO 2 ).
- the insulating film 2 g may contain a high dielectric having a relative dielectric constant higher than that of the silicon oxide.
- the high dielectric is, for example, a metal oxide.
- the conductive layer 21 includes at least one source-side selection gate SGS, a plurality of word lines WL, and at least one drain-side selection gate SGD.
- the source-side selection gate SGS is a gate electrode of a source-side select transistor STS.
- the word line WL is a gate electrode of a memory cell MC.
- the drain-side selection gate SGD is a gate electrode of a drain-side select transistor STD.
- the source-side selection gate SGS is provided in a lower area of the stacked body 2 .
- the drain-side selection gate SGD is provided in an upper area of the stacked body 2 .
- the lower area refers to an area of the stacked body 2 on the side closer to the base body portion 1
- the upper area refers to an area of the stacked body 2 on the side farther from the base body portion 1 .
- the word line WL is provided between the source-side selection gate SGS and the drain-side selection gate SGD.
- a thickness in the Z direction of the insulating layer 22 that insulates the source-side selection gate SGS and the word line WL may be thicker than, for example, a thickness in the Z-axis direction of the insulating layer 22 that insulates the word line WL and the word line WL.
- a cover insulating film may be provided on top of the insulating layer 22 that is farthest from the base body portion 1 .
- the cover insulating film contains, for example, a silicon oxide.
- the semiconductor storage device 100 includes a plurality of memory cells MC connected in series between the source-side select transistor STS and the drain-side select transistor STD.
- a structure in which the source-side select transistor STS, the memory cell MC, and the drain-side select transistor STD are connected in series is generally referred to as a “memory string” or a “NAND string”.
- the memory string is connected to a bit line BL via a via contact V 0 .
- the bit line BL is provided above the stacked body 2 and extends in the Y direction.
- a plurality of deep slits ST and a plurality of shallow slits SHE are respectively provided in the stacked body 2 .
- the “slit” indicates a groove and a portion including a conductor and/or an insulator embedded in the groove.
- the deep slit ST extends in the X direction, penetrates the stacked body 2 from an upper end of the stacked body 2 to the base body portion 1 , and is provided in the stacked body 2 .
- the deep slit ST is filled with, for example, an insulator such as a silicon oxide film.
- the deep slit ST is filled with a conductor that is electrically connected to the semiconductor layer 13 while being electrically insulated from the stacked body 2 by an insulator.
- the insulator covers an inner surface of the slit ST, and further the conductor is embedded inside the insulator.
- a low resistance metal such as tungsten is used for this conductor.
- the conductor is connected to the semiconductor layer 13 in the slit ST.
- the shallow slit SHE extends in the X direction and is provided from the upper end of the stacked body 2 to the middle of the stacked body 2 .
- the shallow slit SHE is filled with, for example, an insulator such as a silicon oxide film.
- the semiconductor storage device 100 includes the memory cell array MCA and the peripheral circuit (the CMOS circuit) located below the memory cell array MCA.
- the semiconductor layer 13 provided between the memory cell array MCA and the peripheral circuit functions as a source layer of the memory cell array MCA.
- FIG. 2 is a cross-sectional view illustrating an example of a configuration of a columnar portion CL.
- Each of the plurality of columnar portions CL is provided in a memory hole MH provided in the stacked body 2 .
- the memory hole MH penetrates the stacked body 2 from the upper end of the stacked body 2 along the Z direction, and is provided in the stacked body 2 and the semiconductor layer 13 .
- Each of the plurality of columnar portions CL includes a semiconductor body 210 , a memory film 220 , and a core layer 230 .
- the semiconductor body 210 is electrically connected to the semiconductor layer 13 .
- the memory film 220 includes a charge trapping portion between the semiconductor body 210 and the conductive layer 21 .
- a plurality of columnar portions CL respectively selected one by one from each finger, which will be described later, are commonly connected to one bit line BL via the via contact V 0 .
- Each of the columnar portions CL is provided in, for example, a memory cell array area.
- FIG. 3 is a plan view illustrating an example of the configuration of the columnar portion CL.
- a shape of the memory hole MH on the XY plane is, for example, a circle or an ellipse.
- a block insulating film 21 a forming a part of the memory film 220 may be provided between the conductive layer 21 and the insulating layer 22 .
- the block insulating film 21 a is, for example, a silicon oxide film or a metal oxide film.
- One example of a metal oxide is an aluminum oxide.
- a barrier film 21 b may be provided between the conductive layer 21 and the insulating layer 22 and between the conductive layer 21 and the memory film 220 .
- the barrier film 21 b when the conductive layer 21 is tungsten, a stacked structure film of a titanium nitride and titanium is selected as the barrier film 21 b .
- the block insulating film 21 a prevents back tunneling of charges from the conductive layer 21 to the side of the memory film 220 .
- the barrier film 21 b improves adhesion between the conductive layer 21 and the block insulating film 21 a.
- a shape of the semiconductor body 210 is, for example, a cylindrical shape having a bottom.
- the semiconductor body 210 contains, for example, silicon. Silicon is, for example, polysilicon obtained by crystallizing amorphous silicon.
- the semiconductor body 210 is, for example, undoped silicon.
- the semiconductor body 210 may also be a p-type silicon.
- the semiconductor body 210 becomes respective channels of the drain-side select transistor STD, the memory cell MC, and the source-side select transistor STS.
- the memory film 220 portions other than the block insulating film 21 a are provided between an inner wall of the memory hole MH and the semiconductor body 210 .
- the memory film 220 has, for example, a cylindrical shape.
- a plurality of memory cells MC have a storage area between the semiconductor body 210 and the conductive layer 21 serving as the word line WL, and are stacked in the Z direction.
- the memory film 220 includes, for example, a cover insulating film 221 , a charge trapping film 222 , and a tunnel insulating film 223 .
- Each of the semiconductor body 210 , the charge trapping film 222 , and the tunnel insulating film 223 extends in the Z direction.
- the cover insulating film 221 is provided between the insulating layer 22 and the charge trapping film 222 .
- the cover insulating film 221 contains, for example, a silicon oxide.
- the cover insulating film 221 protects the charge trapping film 222 from being etched when replacing a sacrifice film (not illustrated) with the conductive layer 21 (a replacement process).
- the cover insulating film 221 may be removed from between the conductive layer 21 and the memory film 220 in the replacement process.
- the block insulating film 21 a is provided between the conductive layer 21 and the charge trapping film 222 .
- the cover insulating film 221 may be omitted.
- the charge trapping film 222 is provided between the block insulating film 21 a , the cover insulating film 221 , and the tunnel insulating film 223 .
- the charge trapping film 222 contains, for example, a silicon nitride, and has a trap site for trapping charges in the film.
- a portion of the charge trapping film 222 interposed between the conductive layer 21 that becomes the word line WL and the semiconductor body 210 forms a storage area of the memory cell MC as a charge trapping portion.
- a threshold voltage of the memory cell MC changes depending on the presence or absence of charges in the charge trapping portion or an amount of charges trapped in the charge trapping portion. Accordingly, the memory cell MC stores information.
- the tunnel insulating film 223 is provided between the semiconductor body 210 and the charge trapping film 222 .
- the tunnel insulating film 223 contains, for example, a silicon oxide, or a silicon oxide and a silicon nitride.
- the tunnel insulating film 223 is a potential barrier between the semiconductor body 210 and the charge trapping film 222 . For example, when injecting an electron from the semiconductor body 210 into the charge trapping portion (in a write operation), and when injecting a hole from the semiconductor body 210 into the charge trapping portion (in an erase operation), the electron and the hole respectively pass through (tunneling) the potential barrier of the tunnel insulating film 223 .
- the core layer 230 embeds an internal space of the cylindrical semiconductor body 210 .
- the core layer 230 has a columnar shape.
- the core layer 230 contains, for example, a silicon oxide, and has insulation properties.
- FIG. 4 is a plan view illustrating an example of the configuration of the semiconductor storage device according to the embodiment.
- the word line WL extends in the X direction and the bit line BL extends in the Y direction.
- a terrace area TRC of the word line WL is provided on opposite sides in the X direction of the memory cell array MCA.
- the terrace area TRC is an area in which the word lines WL are processed into a staircase shape, and connects a contact plug to each word line WL.
- the peripheral circuit such as the CMOS circuit, that controls the memory cell array MCA is provided below the memory cell array MCA.
- FIG. 5 is a plan view illustrating a memory cell array MCA of a frame B 1 in FIG. 4 in more detail.
- Two terrace areas TRC on the opposite sides of the memory cell array MCA are provided, and a cell area RMC and tap areas TAP_BL and TAP_VB are provided in the memory cell array MCA.
- the cell area RMC is an area including a plurality of memory cells MC, and includes a plurality of columnar portions CL.
- the tap area TAP_BL is a contact area for forming a contact plug in order to connect the bit line BL to the CMOS circuit below the memory cell array MCA.
- the tap area TAP_VB is a contact area for forming a contact plug not only for connecting power (not illustrated) to the CMOS circuit but also for connecting a source voltage to the semiconductor layer 13 .
- FIG. 6 is a plan view illustrating the tap area TAP_VB of a frame B 2 in FIG. 5 in more detail.
- the memory cell array MCA includes the cell area RMC and the tap area TAP_VB.
- the tap area TAP_VB is a contact area provided between two adjacent cell areas RMC.
- the deep slit ST includes a conductor slit LI_ST and an insulator slit OXI_ST.
- the conductor slit LI_ST is provided over two adjacent cell areas RMC and the tap area TAP_VB provided between the two cell areas RMC.
- the conductor slit LI_ST continuously extends in the X direction intersecting an extending direction (the Y direction) of the bit line BL (for example, orthogonal to the extending direction (the Y direction) of the bit line BL).
- the Y direction the extending direction
- the bit line BL for example, orthogonal to the extending direction (the Y direction) of the bit line BL.
- the conductor slit LI_ST is coupled to the semiconductor layer 13 as a source layer by penetrating the cell area RMC and the tap area TAP_VB in the stacking direction (the Z direction). Accordingly, the conductor slit LI_ST functions as a contact connected to the semiconductor layer 13 , and can apply a predetermined source voltage to the semiconductor layer 13 from an upper wiring which is not illustrated.
- the conductor slit LI_ST is filled with a conductor (for example, tungsten) that is electrically connected to the semiconductor layer 13 while being electrically insulated from the stacked body 2 by an insulator (for example, a silicon oxide film).
- the insulator slit OXI_ST is provided in the tap area TAP_VB and extends in the X direction approximately parallel along the conductor slit LI_ST.
- Two insulator slits OXI_ST adjacent to each other in the Y direction are provided between the conductor slits LI_ST adjacent to each other in the Y direction, and are arranged on the opposite sides of a contact C 4 so as to sandwich the contact C 4 . That is, the insulator slit OXI_ST is disposed between the conductor slit LI_ST and the contact C 4 in the planar layout.
- the insulator slit OXI_ST is filled with, for example, an insulator such as a silicon oxide film.
- the insulator in the insulator slit OXI_ST may be an air gap.
- the contact C 4 When viewed from the top, the contact C 4 is provided in the tap area TAP_VB, penetrates the tap area TAP_VB in the Z direction, and is provided up to the peripheral circuit therebelow.
- the contact C 4 is provided, for example, in order to supply power to the peripheral circuit.
- a stacked body of an insulating layer having no conductive layer and a sacrifice layer remains between the two adjacent insulator slits OXI_ST, and the contact C 4 penetrates the stacked body of the insulating layer and the sacrifice layer and is connected to the peripheral circuit.
- a low resistance metal such as tungsten is used for the contact C 4 .
- the shallow slit SHE is provided in the two adjacent cell areas RMC and the tap area TAP_VB provided between the two cell areas RMC.
- the shallow slit SHE continuously extends in the X direction intersecting the extending direction (the Y direction) of the bit line BL (for example, orthogonal to the extending direction (the Y direction) of the bit line BL).
- the shallow slit SHE is provided at an upper portion of the cell area RMC and the tap area TAP_VB in the stacking direction (the Z direction), and has a function of isolating the drain-side selection gate SGD.
- the shallow slit SHE may be isolated in the tap area TAP_VB in which the stacked body of the insulating layer and the sacrifice layer is provided.
- a memory cell array interposed between two conductor slits LI_ST adjacent to each other in the Y direction in the cell area RMC is referred to as a block BLK.
- the block BLK forms, for example, a minimum unit of data erase.
- the memory cell array provided not only between the conductor slit LI_ST and the shallow slit SHE but also between the two shallow slits SHE adjacent to each other in the Y direction is referred to as a finger FNG.
- the drain-side selection gate SGD is divided for each finger FNG by the shallow slit SHE or the conductor slit LI_ST.
- the finger FNG forms, for example, a minimum unit of data read or data write. Accordingly, it is possible to selectively access one finger FNG in the block BLK via the drain-side selection gate SGD at the time of the data write and the data read.
- a plurality of bit lines BL are provided on the cell area RMC.
- the bit line BL extends in the Y direction in the planar layout viewed from the stacking direction (the Z direction).
- a low resistance metal such as copper, aluminum, and tungsten is used for the bit line BL.
- the semiconductor storage device 100 further includes wirings M 0 _ 1 and M 0 _ 2 .
- the wiring M 0 _ 1 is a wiring that extends in a direction intersecting an extending direction of the conductor slit LI_ST in the tap area TAP_VB (the Y direction).
- Each of the two wirings M 0 _ 1 is provided along a boundary between the two cell areas RMC on opposite sides of the tap area TAP_VB and the tap area TAP_VB.
- the wiring M 0 _ 1 is commonly connected to a plurality of wirings M 0 _ 2 provided in the tap area TAP_VB.
- the wiring M 0 _ 2 is provided directly above the conductor slit LI_ST in the tap area TAP_VB, and extends along the conductor slit LI_ST in the planar layout viewed from the stacking direction (the Z direction).
- the wiring M 0 _ 2 extends between two wirings M 0 _ 1 provided on the opposite sides of a certain tap area TAP_VB, and connects the two wirings M 0 _ 1 . In this manner, the wirings M 0 _ 1 and M 0 _ 2 are formed in a ladder shape in the planar layout.
- the wirings M 0 _ 1 and M 0 _ 2 are wiring layers at an upper portion of the conductor slit LI_ST and the insulator slit OXI_ST, and are connected to each other.
- a low resistance metal such as copper, aluminum, and tungsten is used for the wirings M 0 _ 1 and M 0 _ 2 .
- the wirings M 0 _ 1 and M 0 _ 2 are formed in the same wiring layer, and are formed in the same process.
- the wirings M 0 _ 1 and M 0 _ 2 and the bit line BL are also formed in the same wiring layer, and are formed in the same process. Accordingly, the wirings M 0 _ 1 and M 0 _ 2 and the bit line BL are formed of the same material.
- An interlayer insulating film is provided between the wirings M 0 _ 1 and M 0 _ 2 and the conductor slit LI_ST.
- a plurality of via contacts V 0 connect the wiring M 0 _ 1 and the conductor slit LI_ST, and also connect the wiring M 0 _ 2 and the conductor slit LI_ST via the interlayer insulating film (not illustrated in FIG. 6 ).
- a low resistance metal such as tungsten is used for the via contact V 0 .
- FIG. 7 is a plan view illustrating a part of a memory cell array of a frame B 3 in FIG. 6 in more detail.
- the columnar portion CL that is, the memory hole MH is disposed, in the planar layout, between two conductor slits LI_ST adjacent to each other in the Y direction in a manner of a hexagonal closest packing arrangement.
- the shallow slit SHE is provided on a part of the columnar portion CL.
- the columnar portion CL below the shallow slit SHE does not form a memory cell.
- FIG. 7 the illustration of the bit line BL is omitted.
- a connection relationship between the columnar portion CL and the bit line BL will be illustrated with reference to FIG. 8 .
- FIG. 8 is a plan view illustrating the connection relationship between the columnar portion CL and the bit line BL.
- the bit line BL is connected to the columnar portion CL via the via contact V 0 .
- the via contacts V 0 are arranged in a staggered manner in the planar layout. Accordingly, each bit line BL is connected to only one columnar portion CL of the plurality of columnar portions CL in a certain finger FNG via the via contact V 0 .
- FIG. 9 is a cross-sectional view taken along a line 9 - 9 in FIG. 7 .
- FIG. 10 is a cross-sectional view taken along a line 10 - 10 in FIG. 7 .
- a semiconductor element such as the transistor Tr is formed on the substrate 10 of the base body portion 1 .
- the semiconductor element such as the transistor Tr forms the peripheral circuit such as the CMOS circuit.
- the peripheral circuit formed on the substrate 10 is covered with an interlayer insulating film ILD 1 .
- the semiconductor layer 13 functioning as a source layer is provided on the interlayer insulating film ILD 1 .
- the stacked body 2 is provided on the semiconductor layer 13 .
- the columnar portion CL penetrates the stacked body 2 and is provided up to the semiconductor layer 13 . Accordingly, the semiconductor body 210 of the columnar portion CL is electrically connected to the semiconductor layer 13 .
- the conductor slit LI_ST also penetrates the stacked body 2 and is provided up to the semiconductor layer 13 .
- the conductor slit LI_ST is provided in a groove that penetrates the stacked body 2 in the stacking direction in the cell area RMC and the tap area TAP_VB, and that is provided up to the semiconductor layer 13 .
- the conductor slit LI_ST includes an insulating layer 40 that covers an inner surface of the groove and a conductor 50 embedded inside the insulating layer 40 .
- the insulating layer 40 is interposed between the conductor 50 and the stacked body 2 , and electrically insulates the conductor 50 from the word line WL, the source-side selection gate SGS, and the drain-side selection gate SGD.
- the conductor 50 is electrically connected to the semiconductor layer 13 at a bottom portion of the conductor slit LI_ST. That is, the conductor 50 is electrically connected to the semiconductor layer 13 in a state of being electrically insulated from the word line WL, the source-side selection gate SGS, and the drain-side selection gate SGD of the stacked body 2 by the insulating layer 40 . Accordingly, the conductor slit LI_ST can apply a source voltage to the semiconductor layer 13 from the wirings M 0 _ 1 and M 0 _ 2 above the stacked body 2 .
- the shallow slit SHE cuts the drain-side selection gate SGD, and divides the columnar portion CL (that is, the memory cell array MCA) into each finger FNG.
- the via contact V 0 is provided between the bit line BL and the columnar portion CL corresponding thereto.
- An interlayer insulating film ILD 2 is provided on the stacked body 2 , and the via contact V 0 is provided in the interlayer insulating film ILD 2 .
- the via contact V 0 may be configured to be divided into a plurality of via contacts V 0 _ 1 and V 0 _ 2 up and down.
- the via contact V 0 _ 1 is, for example, a contact having a relatively wide (thick) width that is provided on all the columnar portions CL forming the memory cell MC.
- the via contact V 0 _ 2 is selectively provided on the via contact V 0 _ 1 , and is a contact having a relatively narrow (thin) width that electrically connects the bit line BL and the columnar portion CL corresponding thereto.
- a low resistance metal such as tungsten is used for the via contacts V 0 _ 1 and V 0 _ 2 .
- the via contact V 0 illustrated in FIG. 8 shows the planar layout of the via contact V 0 _ 2 .
- FIG. 11 is a plan view illustrating a part of a tap area TAP_VB of a frame B 4 in FIG. 6 in more detail.
- the via contact V 0 connects the bit line BL and the columnar portion CL in the cell area RMC.
- the via contact V 0 is provided between the conductor slit LI_ST and the wiring M 0 _ 2 thereabove, and electrically connects the conductor slit LI_ST and the wiring M 0 _ 2 .
- a plurality of via contacts V 0 are arranged in the X direction along the conductor slit LI_ST and the wiring M 0 _ 2 .
- the via contact V 0 is also provided in an intersecting area R M 0 LI of the conductor slit LI_ST and the wiring M 0 _ 1 , and electrically connects the conductor slit LI_ST and the wiring M 0 _ 1 .
- the via contact V 0 may be provided only between the conductor slit LI_ST and the wiring M 0 _ 2 .
- FIG. 12 is a cross-sectional view taken along a line 12 - 12 in FIG. 11 .
- FIG. 13 is a cross-sectional view taken along a line 13 - 13 in FIG. 11 .
- FIG. 14 is a cross-sectional view taken along a line 14 - 14 in FIG. 11 .
- the conductor slit LI_ST, the columnar portion CL, and the shallow slit SHE are provided in the same manner as that of the cell area RMC.
- the columnar portion CL does not function as the memory cell MC.
- the via contact V 0 is provided on the conductor slit LI_ST, and electrically connects the conductor slit LI_ST and the wiring M 0 _ 1 or the wiring M 0 _ 2 .
- a plurality of via contacts V 0 are arranged along the wiring M 0 _ 2 .
- the via contact V 0 is provided in the interlayer insulating film ILD 2 and electrically connects the conductor slit LI_ST and the wiring M 0 _ 2 .
- the wiring M 0 _ 2 extends approximately parallel along the conductor slit LI_ST above the conductor slit LI_ST.
- the conductor slit LI_ST is a plate-shaped member provided from an upper surface of the stacked body 2 to the semiconductor layer 13 .
- the insulator slit OXI_ST in FIG. 13 is provided between the contact C 4 and the conductor slit LI_ST.
- the insulator slit OXI_ST is embedded in a groove that penetrates the stacked body 2 of the tap area TAP_VB in the stacking direction (the Z direction), and that is provided up to the semiconductor layer 13 .
- the stacked body of the insulating layer 22 and a sacrifice layer SAC remains between the two adjacent insulator slits OXI_ST in the tap area TAP_VB.
- the sacrifice layer SAC is, for example, a silicon nitride film.
- the sacrifice layer SAC is replaced with the conductive layer 21 (for example, tungsten) and replaced with the word line WL.
- the insulator slit OXI_ST prevents etching of the sacrifice layer SAC, and the sacrifice layer SAC remains without being replaced therewith.
- the contact C 4 is provided in the stacked body of the sacrifice layer SAC and the insulating layer 22 .
- the contact C 4 penetrates the stacked body of the insulating layer 22 and the sacrifice layer SAC and is connected to any wiring of the peripheral circuit.
- a low resistance metal such as tungsten is used for the contact C 4 .
- the semiconductor storage device 100 includes, in the tap area TAP_VB, the wiring M 0 _ 1 extending in the Y direction; and the wiring M 0 _ 2 extending in the X direction and provided directly above the conductor slit LI_ST.
- a plurality of via contacts V 0 are provided at least between the wiring M 0 _ 2 and the conductor slit LI_ST. Accordingly, the wiring M 0 _ 2 and the conductor slit LI_ST are connected to each other with low resistance. Therefore, even though a relatively large source current flows, the source current dispersedly flows through a plurality of via contacts V 0 .
- This arrangement can prevent melting of the via contact V 0 provided between the conductor slit LI_ST as a wiring connected to the semiconductor layer 13 and the wirings M 0 _ 1 and M 0 _ 2 .
- the semiconductor storage device 100 of the embodiment includes the wiring M 0 _ 2 , and a relatively large number of via contacts V 0 can be provided between the wiring M 0 _ 2 and the conductor slit LI_ST. Accordingly, even though the large source current flows, melting of the via contact V 0 provided between the conductor slit LI_ST and the wirings M 0 _ 1 and M 0 _ 2 can be prevented.
- the conductor slit LI_ST When all the portions other than the insulating layer of the conductor slit LI_ST are filled with the low resistance metal such as tungsten, the conductor slit LI_ST has low resistance, thereby making it possible to allow the large source current to flow. What is described above accelerates the melting of the via contact V 0 . Therefore, when all the conductor portions of the conductor slit LI_ST are filled with the low resistance metal, particularly, a configuration according to the embodiment is effective for preventing the melting of the via contact V 0 .
- FIG. 15 is a plan view illustrating an example of a configuration of a semiconductor storage device according to a first modification.
- each of the wirings M 0 _ 2 is isolatedly provided in a cell area RMCa on one side of the tap area TAP_VB and a cell area RMCb on the other side of the tap area TAP_VB.
- Other configurations of the first modification may be the same as the corresponding configurations of the above-described embodiment.
- the wiring M 0 _ 2 is isolated, a problem does not occur because the wiring M 0 _ 2 is connected to the wiring M 0 _ 1 via the via contact V 0 with low resistance.
- FIG. 16 is a plan view illustrating an example of a configuration of a semiconductor storage device according to a second modification.
- the via contact V 0 is arranged in the X direction over the whole wiring M 0 _ 2 . Accordingly, the resistance between the wiring M 0 _ 2 and the conductor slit LI_ST becomes further lower.
- Other configurations of the second modification may be the same as the corresponding configurations of the above-described embodiment.
- the via contact V 0 may be arranged in the whole wiring M 0 _ 2 .
- the size and the number of via contacts V 0 may be set according to the current flowing through the via contacts V 0 .
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Abstract
Description
- This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-005851, filed Jan. 17, 2020, the entire contents of which are incorporated herein by reference.
- Embodiments described herein relate generally to a semiconductor storage device.
- In recent years, a semiconductor storage device including a three-dimensional memory cell array is developed. Memory cells of such a semiconductor storage device are three-dimensionally arranged. In the semiconductor storage device, a local wiring that connects a source layer provided below the memory cell array to an upper wiring is provided in a tap area between the adjacent memory cell arrays. The local wiring is formed by embedding a low resistance metal such as tungsten in a groove (a slit) in the tap area to prevent warpage of a substrate and to allow formation concurrently with contacts.
- In addition, a current from the source layer flows from the local wiring to the upper wiring via a via contact. The current concentrates on the via contact between the local wiring and the upper wiring, which may melt the via contact.
-
FIG. 1 is a perspective view illustrating an example of a configuration of a semiconductor storage device. -
FIG. 2 is a cross-sectional view illustrating an example of a configuration of a columnar portion. -
FIG. 3 is a plan view illustrating an example of the configuration of the columnar portion. -
FIG. 4 is a plan view illustrating an example of the configuration of the semiconductor storage device according to the embodiment. -
FIG. 5 is a plan view illustrating a memory cell array of a frame B1 inFIG. 4 in more detail. -
FIG. 6 is a plan view illustrating a tap area of a frame B2 inFIG. 5 in more detail. -
FIG. 7 is a plan view illustrating a part of a memory cell array of a frame B3 inFIG. 6 in more detail. -
FIG. 8 is a plan view illustrating a connection relationship between the columnar portion and a bit line. -
FIG. 9 is a cross-sectional view taken along a line 9-9 inFIG. 7 . -
FIG. 10 is a cross-sectional view taken along a line 10-10 inFIG. 7 . -
FIG. 11 is a plan view illustrating a part of a tap area of a frame B4 inFIG. 6 in more detail. -
FIG. 12 is a cross-sectional view taken along a line 12-12 inFIG. 11 . -
FIG. 13 is a cross-sectional view taken along a line 13-13 inFIG. 11 . -
FIG. 14 is a cross-sectional view taken along a line 14-14 inFIG. 11 . -
FIG. 15 is a plan view illustrating an example of a configuration of a semiconductor storage device according to a first modification. -
FIG. 16 is a plan view illustrating an example of a configuration of a semiconductor storage device according to a second modification. - Embodiments provide a semiconductor storage device capable of preventing melting of a via contact between a local wiring connected to a source layer and an upper wiring thereabove.
- In general, according to one embodiment, a semiconductor storage device includes: a memory cell array including a stacked body having a plurality of insulating layers and a plurality of conductive layers are alternately stacked, wherein the memory cell array includes a cell area that includes a plurality of memory cells and a contact area provided adjacent the cell area; a circuit provided below the memory cell array; a source layer provided between the memory cell array and the circuit; a first contact provided in the contact area, and coupled to the circuit by extending along a stacking direction of the stacked body; a second contact provided over the cell area and the contact area, and coupled to the source layer by extending along the stacking direction; a first wiring extending in a direction intersecting an extending direction of the second contact in the contact area; a second wiring provided above the second contact, extending along the second contact in the contact area, and connected to the first wiring; and a plurality of third contacts provided between the second wiring and the second contact.
- Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings. The embodiment does not limit the present disclosure. In the following embodiment, a vertical direction of a semiconductor substrate indicates a relative direction when a surface on which a semiconductor element is provided is defined as UP, and may be different from a vertical direction according to acceleration of gravity. The drawings are schematic or conceptual, and a proportion of each portion is not necessarily the same as that of the actual one. In the specification and drawings, the same elements as those described above with reference to the already illustrated drawings will be denoted by the same reference signs, and detailed description thereof will be appropriately omitted.
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FIG. 1 is a perspective view illustrating an example of a configuration of a semiconductor storage device. Asemiconductor storage device 100 may be, for example, a NAND type flash memory including a three-dimensional memory cell array MCA in which memory cells are three-dimensionally arranged. In the embodiment, a stacking direction of astacked body 2 is defined as a Z direction. A direction that intersects the Z direction (for example, that is orthogonal the Z direction) is defined as a Y direction. A direction that intersects each of the Z and Y directions (for example, that is orthogonal to each of the Z and Y directions) is defined as an X direction. - The
semiconductor storage device 100 includesabase body portion 1, thestacked body 2, and a plurality of columnar portions CL. - The
base body portion 1 includes asubstrate 10, aninsulating film 11, aconductive film 12, and asemiconductor layer 13. Theinsulating film 11 is provided on thesubstrate 10. Theconductive film 12 is provided on theinsulating film 11. Thesemiconductor layer 13 is provided on theconductive film 12. Thesubstrate 10 is a semiconductor substrate, for example, a p-type silicon substrate. For example, anelement isolation area 10 i is provided in a front surface area of thesubstrate 10. Theelement isolation area 10 i is, for example, an insulating area containing a silicon oxide, and partitions an active area AA in the front surface area of thesubstrate 10. A source area and a drain area of a transistor Tr are provided in the active area AA. The transistor Tr forms a peripheral circuit (for example, a complementary metal oxide semiconductor (CMOS) circuit) of the nonvolatile memory. Theinsulating film 11 contains, for example, silicon oxide (SiO2), and insulates the transistor Tr. Awiring 11 a is provided in theinsulating film 11. Thewiring 11 a is a wiring electrically connected to the transistor Tr. Theconductive film 12 contains a conductive metal such as tungsten (W). Thesemiconductor layer 13 contains, for example, silicon. A conductivity type of silicon is, for example, an n-type. A part of thesemiconductor layer 13 may contain undoped silicon. - The stacked
body 2 is located in the Z direction with respect to thesemiconductor layer 13. The stackedbody 2 is configured such that a plurality ofconductive layers 21 and a plurality ofinsulating layers 22 are alternately stacked along the Z direction. Theconductive layer 21 contains a conductive metal, such as tungsten. For example, theinsulating layer 22 contains a silicon oxide. Theinsulating layer 22 insulates theconductive layers 21 from each other. The number of layers of each of theconductive layer 21 and theinsulating layer 22 is freely selected. Theinsulating layer 22 may be, for example, an air gap. For example, an insulatingfilm 2 g is provided between thestacked body 2 and thesemiconductor layer 13. The insulatingfilm 2 g contains, for example, a silicon oxide (SiO2). The insulatingfilm 2 g may contain a high dielectric having a relative dielectric constant higher than that of the silicon oxide. The high dielectric is, for example, a metal oxide. - The
conductive layer 21 includes at least one source-side selection gate SGS, a plurality of word lines WL, and at least one drain-side selection gate SGD. The source-side selection gate SGS is a gate electrode of a source-side select transistor STS. The word line WL is a gate electrode of a memory cell MC. The drain-side selection gate SGD is a gate electrode of a drain-side select transistor STD. The source-side selection gate SGS is provided in a lower area of thestacked body 2. The drain-side selection gate SGD is provided in an upper area of thestacked body 2. The lower area refers to an area of thestacked body 2 on the side closer to thebase body portion 1, and the upper area refers to an area of thestacked body 2 on the side farther from thebase body portion 1. The word line WL is provided between the source-side selection gate SGS and the drain-side selection gate SGD. - Among the plurality of insulating
layers 22, a thickness in the Z direction of the insulatinglayer 22 that insulates the source-side selection gate SGS and the word line WL may be thicker than, for example, a thickness in the Z-axis direction of the insulatinglayer 22 that insulates the word line WL and the word line WL. A cover insulating film may be provided on top of the insulatinglayer 22 that is farthest from thebase body portion 1. The cover insulating film contains, for example, a silicon oxide. - The
semiconductor storage device 100 includes a plurality of memory cells MC connected in series between the source-side select transistor STS and the drain-side select transistor STD. A structure in which the source-side select transistor STS, the memory cell MC, and the drain-side select transistor STD are connected in series is generally referred to as a “memory string” or a “NAND string”. For example, the memory string is connected to a bit line BL via a via contact V0. The bit line BL is provided above thestacked body 2 and extends in the Y direction. - A plurality of deep slits ST and a plurality of shallow slits SHE are respectively provided in the
stacked body 2. The “slit” indicates a groove and a portion including a conductor and/or an insulator embedded in the groove. The deep slit ST extends in the X direction, penetrates thestacked body 2 from an upper end of thestacked body 2 to thebase body portion 1, and is provided in thestacked body 2. Although not illustrated inFIG. 1 , the deep slit ST is filled with, for example, an insulator such as a silicon oxide film. Alternatively, the deep slit ST is filled with a conductor that is electrically connected to thesemiconductor layer 13 while being electrically insulated from thestacked body 2 by an insulator. That is, the insulator covers an inner surface of the slit ST, and further the conductor is embedded inside the insulator. For example, a low resistance metal such as tungsten is used for this conductor. The conductor is connected to thesemiconductor layer 13 in the slit ST. The shallow slit SHE extends in the X direction and is provided from the upper end of thestacked body 2 to the middle of thestacked body 2. Although not illustrated inFIG. 1 , the shallow slit SHE is filled with, for example, an insulator such as a silicon oxide film. - As described above, the
semiconductor storage device 100 according to the embodiment includes the memory cell array MCA and the peripheral circuit (the CMOS circuit) located below the memory cell array MCA. Thesemiconductor layer 13 provided between the memory cell array MCA and the peripheral circuit functions as a source layer of the memory cell array MCA. -
FIG. 2 is a cross-sectional view illustrating an example of a configuration of a columnar portion CL. Each of the plurality of columnar portions CL is provided in a memory hole MH provided in thestacked body 2. The memory hole MH penetrates thestacked body 2 from the upper end of thestacked body 2 along the Z direction, and is provided in thestacked body 2 and thesemiconductor layer 13. Each of the plurality of columnar portions CL includes asemiconductor body 210, amemory film 220, and acore layer 230. Thesemiconductor body 210 is electrically connected to thesemiconductor layer 13. Thememory film 220 includes a charge trapping portion between thesemiconductor body 210 and theconductive layer 21. A plurality of columnar portions CL respectively selected one by one from each finger, which will be described later, are commonly connected to one bit line BL via the via contact V0. Each of the columnar portions CL is provided in, for example, a memory cell array area. -
FIG. 3 is a plan view illustrating an example of the configuration of the columnar portion CL. A shape of the memory hole MH on the XY plane is, for example, a circle or an ellipse. Ablock insulating film 21 a forming a part of thememory film 220 may be provided between theconductive layer 21 and the insulatinglayer 22. Theblock insulating film 21 a is, for example, a silicon oxide film or a metal oxide film. One example of a metal oxide is an aluminum oxide. Abarrier film 21 b may be provided between theconductive layer 21 and the insulatinglayer 22 and between theconductive layer 21 and thememory film 220. For example, when theconductive layer 21 is tungsten, a stacked structure film of a titanium nitride and titanium is selected as thebarrier film 21 b. Theblock insulating film 21 a prevents back tunneling of charges from theconductive layer 21 to the side of thememory film 220. Thebarrier film 21 b improves adhesion between theconductive layer 21 and theblock insulating film 21 a. - A shape of the
semiconductor body 210 is, for example, a cylindrical shape having a bottom. Thesemiconductor body 210 contains, for example, silicon. Silicon is, for example, polysilicon obtained by crystallizing amorphous silicon. Thesemiconductor body 210 is, for example, undoped silicon. Thesemiconductor body 210 may also be a p-type silicon. Thesemiconductor body 210 becomes respective channels of the drain-side select transistor STD, the memory cell MC, and the source-side select transistor STS. - In the
memory film 220, portions other than theblock insulating film 21 a are provided between an inner wall of the memory hole MH and thesemiconductor body 210. Thememory film 220 has, for example, a cylindrical shape. A plurality of memory cells MC have a storage area between thesemiconductor body 210 and theconductive layer 21 serving as the word line WL, and are stacked in the Z direction. Thememory film 220 includes, for example, acover insulating film 221, acharge trapping film 222, and atunnel insulating film 223. Each of thesemiconductor body 210, thecharge trapping film 222, and thetunnel insulating film 223 extends in the Z direction. - The
cover insulating film 221 is provided between the insulatinglayer 22 and thecharge trapping film 222. Thecover insulating film 221 contains, for example, a silicon oxide. Thecover insulating film 221 protects thecharge trapping film 222 from being etched when replacing a sacrifice film (not illustrated) with the conductive layer 21 (a replacement process). Thecover insulating film 221 may be removed from between theconductive layer 21 and thememory film 220 in the replacement process. In this case, as illustrated inFIGS. 2 and 3 , for example, theblock insulating film 21 a is provided between theconductive layer 21 and thecharge trapping film 222. When the replacement process is not used for forming theconductive layer 21, thecover insulating film 221 may be omitted. - The
charge trapping film 222 is provided between theblock insulating film 21 a, thecover insulating film 221, and thetunnel insulating film 223. Thecharge trapping film 222 contains, for example, a silicon nitride, and has a trap site for trapping charges in the film. A portion of thecharge trapping film 222 interposed between theconductive layer 21 that becomes the word line WL and thesemiconductor body 210 forms a storage area of the memory cell MC as a charge trapping portion. A threshold voltage of the memory cell MC changes depending on the presence or absence of charges in the charge trapping portion or an amount of charges trapped in the charge trapping portion. Accordingly, the memory cell MC stores information. - The
tunnel insulating film 223 is provided between thesemiconductor body 210 and thecharge trapping film 222. Thetunnel insulating film 223 contains, for example, a silicon oxide, or a silicon oxide and a silicon nitride. Thetunnel insulating film 223 is a potential barrier between thesemiconductor body 210 and thecharge trapping film 222. For example, when injecting an electron from thesemiconductor body 210 into the charge trapping portion (in a write operation), and when injecting a hole from thesemiconductor body 210 into the charge trapping portion (in an erase operation), the electron and the hole respectively pass through (tunneling) the potential barrier of thetunnel insulating film 223. - The
core layer 230 embeds an internal space of thecylindrical semiconductor body 210. For example, thecore layer 230 has a columnar shape. Thecore layer 230 contains, for example, a silicon oxide, and has insulation properties. -
FIG. 4 is a plan view illustrating an example of the configuration of the semiconductor storage device according to the embodiment. In thesemiconductor storage device 100, in the same manner as that ofFIG. 1 , the word line WL extends in the X direction and the bit line BL extends in the Y direction. A terrace area TRC of the word line WL is provided on opposite sides in the X direction of the memory cell array MCA. The terrace area TRC is an area in which the word lines WL are processed into a staircase shape, and connects a contact plug to each word line WL. As illustrated inFIG. 1 , the peripheral circuit, such as the CMOS circuit, that controls the memory cell array MCA is provided below the memory cell array MCA. -
FIG. 5 is a plan view illustrating a memory cell array MCA of a frame B1 inFIG. 4 in more detail. Two terrace areas TRC on the opposite sides of the memory cell array MCA are provided, and a cell area RMC and tap areas TAP_BL and TAP_VB are provided in the memory cell array MCA. The cell area RMC is an area including a plurality of memory cells MC, and includes a plurality of columnar portions CL. The tap area TAP_BL is a contact area for forming a contact plug in order to connect the bit line BL to the CMOS circuit below the memory cell array MCA. The tap area TAP_VB is a contact area for forming a contact plug not only for connecting power (not illustrated) to the CMOS circuit but also for connecting a source voltage to thesemiconductor layer 13. -
FIG. 6 is a plan view illustrating the tap area TAP_VB of a frame B2 inFIG. 5 in more detail. As described above, the memory cell array MCA includes the cell area RMC and the tap area TAP_VB. The tap area TAP_VB is a contact area provided between two adjacent cell areas RMC. - The deep slit ST includes a conductor slit LI_ST and an insulator slit OXI_ST. In a planar layout viewed from the stacking direction of the stacked body 2 (the Z direction), the conductor slit LI_ST is provided over two adjacent cell areas RMC and the tap area TAP_VB provided between the two cell areas RMC. In the planar layout, the conductor slit LI_ST continuously extends in the X direction intersecting an extending direction (the Y direction) of the bit line BL (for example, orthogonal to the extending direction (the Y direction) of the bit line BL). As will be illustrated later with reference to
FIG. 9 , the conductor slit LI_ST is coupled to thesemiconductor layer 13 as a source layer by penetrating the cell area RMC and the tap area TAP_VB in the stacking direction (the Z direction). Accordingly, the conductor slit LI_ST functions as a contact connected to thesemiconductor layer 13, and can apply a predetermined source voltage to thesemiconductor layer 13 from an upper wiring which is not illustrated. The conductor slit LI_ST is filled with a conductor (for example, tungsten) that is electrically connected to thesemiconductor layer 13 while being electrically insulated from thestacked body 2 by an insulator (for example, a silicon oxide film). - In the planar layout viewed from the top, the insulator slit OXI_ST is provided in the tap area TAP_VB and extends in the X direction approximately parallel along the conductor slit LI_ST. Two insulator slits OXI_ST adjacent to each other in the Y direction are provided between the conductor slits LI_ST adjacent to each other in the Y direction, and are arranged on the opposite sides of a contact C4 so as to sandwich the contact C4. That is, the insulator slit OXI_ST is disposed between the conductor slit LI_ST and the contact C4 in the planar layout. The insulator slit OXI_ST is filled with, for example, an insulator such as a silicon oxide film. The insulator in the insulator slit OXI_ST may be an air gap.
- When viewed from the top, the contact C4 is provided in the tap area TAP_VB, penetrates the tap area TAP_VB in the Z direction, and is provided up to the peripheral circuit therebelow. The contact C4 is provided, for example, in order to supply power to the peripheral circuit. A stacked body of an insulating layer having no conductive layer and a sacrifice layer remains between the two adjacent insulator slits OXI_ST, and the contact C4 penetrates the stacked body of the insulating layer and the sacrifice layer and is connected to the peripheral circuit. For example, a low resistance metal such as tungsten is used for the contact C4.
- In the planar layout viewed from the top, the shallow slit SHE is provided in the two adjacent cell areas RMC and the tap area TAP_VB provided between the two cell areas RMC. In the planar layout, the shallow slit SHE continuously extends in the X direction intersecting the extending direction (the Y direction) of the bit line BL (for example, orthogonal to the extending direction (the Y direction) of the bit line BL). The shallow slit SHE is provided at an upper portion of the cell area RMC and the tap area TAP_VB in the stacking direction (the Z direction), and has a function of isolating the drain-side selection gate SGD. Therefore, in the tap area TAP_VB in which the
stacked body 2 including the conductive layer is provided, a part of the shallow slits SHE is continuously provided in the planar layout. However, as shown in the isolated shallow slit SHE provided between the insulator slits OXI_ST inFIG. 6 , the shallow slit SHE may be isolated in the tap area TAP_VB in which the stacked body of the insulating layer and the sacrifice layer is provided. - A memory cell array interposed between two conductor slits LI_ST adjacent to each other in the Y direction in the cell area RMC is referred to as a block BLK. The block BLK forms, for example, a minimum unit of data erase. In the cell area RMC, the memory cell array provided not only between the conductor slit LI_ST and the shallow slit SHE but also between the two shallow slits SHE adjacent to each other in the Y direction is referred to as a finger FNG. The drain-side selection gate SGD is divided for each finger FNG by the shallow slit SHE or the conductor slit LI_ST. The finger FNG forms, for example, a minimum unit of data read or data write. Accordingly, it is possible to selectively access one finger FNG in the block BLK via the drain-side selection gate SGD at the time of the data write and the data read.
- A plurality of bit lines BL are provided on the cell area RMC. The bit line BL extends in the Y direction in the planar layout viewed from the stacking direction (the Z direction). For example, a low resistance metal such as copper, aluminum, and tungsten is used for the bit line BL.
- The
semiconductor storage device 100 according to the embodiment further includes wirings M0_1 and M0_2. In the planar layout viewed from the stacking direction (the Z direction), the wiring M0_1 is a wiring that extends in a direction intersecting an extending direction of the conductor slit LI_ST in the tap area TAP_VB (the Y direction). Each of the two wirings M0_1 is provided along a boundary between the two cell areas RMC on opposite sides of the tap area TAP_VB and the tap area TAP_VB. The wiring M0_1 is commonly connected to a plurality of wirings M0_2 provided in the tap area TAP_VB. - The wiring M0_2 is provided directly above the conductor slit LI_ST in the tap area TAP_VB, and extends along the conductor slit LI_ST in the planar layout viewed from the stacking direction (the Z direction). The wiring M0_2 extends between two wirings M0_1 provided on the opposite sides of a certain tap area TAP_VB, and connects the two wirings M0_1. In this manner, the wirings M0_1 and M0_2 are formed in a ladder shape in the planar layout.
- The wirings M0_1 and M0_2 are wiring layers at an upper portion of the conductor slit LI_ST and the insulator slit OXI_ST, and are connected to each other. For example, a low resistance metal such as copper, aluminum, and tungsten is used for the wirings M0_1 and M0_2.
- The wirings M0_1 and M0_2 are formed in the same wiring layer, and are formed in the same process. The wirings M0_1 and M0_2 and the bit line BL are also formed in the same wiring layer, and are formed in the same process. Accordingly, the wirings M0_1 and M0_2 and the bit line BL are formed of the same material.
- An interlayer insulating film is provided between the wirings M0_1 and M0_2 and the conductor slit LI_ST. In the tap area TAP_VB, a plurality of via contacts V0 connect the wiring M0_1 and the conductor slit LI_ST, and also connect the wiring M0_2 and the conductor slit LI_ST via the interlayer insulating film (not illustrated in
FIG. 6 ). For example, a low resistance metal such as tungsten is used for the via contact V0. -
FIG. 7 is a plan view illustrating a part of a memory cell array of a frame B3 inFIG. 6 in more detail. The columnar portion CL, that is, the memory hole MH is disposed, in the planar layout, between two conductor slits LI_ST adjacent to each other in the Y direction in a manner of a hexagonal closest packing arrangement. The shallow slit SHE is provided on a part of the columnar portion CL. The columnar portion CL below the shallow slit SHE does not form a memory cell. InFIG. 7 , the illustration of the bit line BL is omitted. A connection relationship between the columnar portion CL and the bit line BL will be illustrated with reference toFIG. 8 . -
FIG. 8 is a plan view illustrating the connection relationship between the columnar portion CL and the bit line BL. The bit line BL is connected to the columnar portion CL via the via contact V0. The via contacts V0 are arranged in a staggered manner in the planar layout. Accordingly, each bit line BL is connected to only one columnar portion CL of the plurality of columnar portions CL in a certain finger FNG via the via contact V0. -
FIG. 9 is a cross-sectional view taken along a line 9-9 inFIG. 7 .FIG. 10 is a cross-sectional view taken along a line 10-10 inFIG. 7 . As illustrated with reference toFIG. 1 , a semiconductor element such as the transistor Tr is formed on thesubstrate 10 of thebase body portion 1. The semiconductor element such as the transistor Tr forms the peripheral circuit such as the CMOS circuit. The peripheral circuit formed on thesubstrate 10 is covered with an interlayer insulating film ILD1. Thesemiconductor layer 13 functioning as a source layer is provided on the interlayer insulating film ILD1. - The
stacked body 2 is provided on thesemiconductor layer 13. The columnar portion CL penetrates thestacked body 2 and is provided up to thesemiconductor layer 13. Accordingly, thesemiconductor body 210 of the columnar portion CL is electrically connected to thesemiconductor layer 13. - The conductor slit LI_ST also penetrates the
stacked body 2 and is provided up to thesemiconductor layer 13. The conductor slit LI_ST is provided in a groove that penetrates thestacked body 2 in the stacking direction in the cell area RMC and the tap area TAP_VB, and that is provided up to thesemiconductor layer 13. The conductor slit LI_ST includes an insulatinglayer 40 that covers an inner surface of the groove and a conductor 50 embedded inside the insulatinglayer 40. The insulatinglayer 40 is interposed between the conductor 50 and thestacked body 2, and electrically insulates the conductor 50 from the word line WL, the source-side selection gate SGS, and the drain-side selection gate SGD. On the other hand, the conductor 50 is electrically connected to thesemiconductor layer 13 at a bottom portion of the conductor slit LI_ST. That is, the conductor 50 is electrically connected to thesemiconductor layer 13 in a state of being electrically insulated from the word line WL, the source-side selection gate SGS, and the drain-side selection gate SGD of thestacked body 2 by the insulatinglayer 40. Accordingly, the conductor slit LI_ST can apply a source voltage to thesemiconductor layer 13 from the wirings M0_1 and M0_2 above thestacked body 2. - The shallow slit SHE cuts the drain-side selection gate SGD, and divides the columnar portion CL (that is, the memory cell array MCA) into each finger FNG.
- The via contact V0 is provided between the bit line BL and the columnar portion CL corresponding thereto. An interlayer insulating film ILD2 is provided on the
stacked body 2, and the via contact V0 is provided in the interlayer insulating film ILD2. The via contact V0 may be configured to be divided into a plurality of via contacts V0_1 and V0_2 up and down. The via contact V0_1 is, for example, a contact having a relatively wide (thick) width that is provided on all the columnar portions CL forming the memory cell MC. The via contact V0_2 is selectively provided on the via contact V0_1, and is a contact having a relatively narrow (thin) width that electrically connects the bit line BL and the columnar portion CL corresponding thereto. For example, a low resistance metal such as tungsten is used for the via contacts V0_1 and V0_2. The via contact V0 illustrated inFIG. 8 shows the planar layout of the via contact V0_2. -
FIG. 11 is a plan view illustrating a part of a tap area TAP_VB of a frame B4 inFIG. 6 in more detail. The via contact V0 connects the bit line BL and the columnar portion CL in the cell area RMC. In the tap area TAP_VB, the via contact V0 is provided between the conductor slit LI_ST and the wiring M0_2 thereabove, and electrically connects the conductor slit LI_ST and the wiring M0_2. A plurality of via contacts V0 are arranged in the X direction along the conductor slit LI_ST and the wiring M0_2. - In the embodiment, the via contact V0 is also provided in an intersecting area R M0 LI of the conductor slit LI_ST and the wiring M0_1, and electrically connects the conductor slit LI_ST and the wiring M0_1. However, as long as the via contact V0 can connect the conductor slit LI_ST and the wiring M0_2 with low resistance, the via contact V0 may be provided only between the conductor slit LI_ST and the wiring M0_2.
-
FIG. 12 is a cross-sectional view taken along a line 12-12 inFIG. 11 .FIG. 13 is a cross-sectional view taken along a line 13-13 inFIG. 11 .FIG. 14 is a cross-sectional view taken along a line 14-14 inFIG. 11 . - As illustrated in
FIGS. 12 and 13 , even in the tap area TAP_VB, the conductor slit LI_ST, the columnar portion CL, and the shallow slit SHE are provided in the same manner as that of the cell area RMC. However, the columnar portion CL does not function as the memory cell MC. - The via contact V0 is provided on the conductor slit LI_ST, and electrically connects the conductor slit LI_ST and the wiring M0_1 or the wiring M0_2. As illustrated in
FIG. 14 , a plurality of via contacts V0 are arranged along the wiring M0_2. The via contact V0 is provided in the interlayer insulating film ILD2 and electrically connects the conductor slit LI_ST and the wiring M0_2. Referring toFIG. 14 , it can be seen that the wiring M0_2 extends approximately parallel along the conductor slit LI_ST above the conductor slit LI_ST. It can be seen that the conductor slit LI_ST is a plate-shaped member provided from an upper surface of thestacked body 2 to thesemiconductor layer 13. - The insulator slit OXI_ST in
FIG. 13 is provided between the contact C4 and the conductor slit LI_ST. The insulator slit OXI_ST is embedded in a groove that penetrates thestacked body 2 of the tap area TAP_VB in the stacking direction (the Z direction), and that is provided up to thesemiconductor layer 13. The stacked body of the insulatinglayer 22 and a sacrifice layer SAC remains between the two adjacent insulator slits OXI_ST in the tap area TAP_VB. The sacrifice layer SAC is, for example, a silicon nitride film. In the cell area RMC, the sacrifice layer SAC is replaced with the conductive layer 21 (for example, tungsten) and replaced with the word line WL. However, between the insulator slits OXI_ST in the tap area TAP_VB, the insulator slit OXI_ST prevents etching of the sacrifice layer SAC, and the sacrifice layer SAC remains without being replaced therewith. - The contact C4 is provided in the stacked body of the sacrifice layer SAC and the insulating
layer 22. The contact C4 penetrates the stacked body of the insulatinglayer 22 and the sacrifice layer SAC and is connected to any wiring of the peripheral circuit. For example, a low resistance metal such as tungsten is used for the contact C4. - As described above, the
semiconductor storage device 100 according to the embodiment includes, in the tap area TAP_VB, the wiring M0_1 extending in the Y direction; and the wiring M0_2 extending in the X direction and provided directly above the conductor slit LI_ST. A plurality of via contacts V0 are provided at least between the wiring M0_2 and the conductor slit LI_ST. Accordingly, the wiring M0_2 and the conductor slit LI_ST are connected to each other with low resistance. Therefore, even though a relatively large source current flows, the source current dispersedly flows through a plurality of via contacts V0. This arrangement can prevent melting of the via contact V0 provided between the conductor slit LI_ST as a wiring connected to thesemiconductor layer 13 and the wirings M0_1 and M0_2. - When the wiring M0_2 is not provided and the via contact V0 is provided only in the intersecting area between the wiring M0_1 and the conductor slit LI_ST, a resistance value between the wiring M0_1 and the conductor slit LI_ST may become relatively high. Therefore, even though a plurality of via contacts V0 are provided, the via contacts V0 may be melted by the large source current.
- On the other hand, the
semiconductor storage device 100 of the embodiment includes the wiring M0_2, and a relatively large number of via contacts V0 can be provided between the wiring M0_2 and the conductor slit LI_ST. Accordingly, even though the large source current flows, melting of the via contact V0 provided between the conductor slit LI_ST and the wirings M0_1 and M0_2 can be prevented. - When all the portions other than the insulating layer of the conductor slit LI_ST are filled with the low resistance metal such as tungsten, the conductor slit LI_ST has low resistance, thereby making it possible to allow the large source current to flow. What is described above accelerates the melting of the via contact V0. Therefore, when all the conductor portions of the conductor slit LI_ST are filled with the low resistance metal, particularly, a configuration according to the embodiment is effective for preventing the melting of the via contact V0.
-
FIG. 15 is a plan view illustrating an example of a configuration of a semiconductor storage device according to a first modification. In the first modification, each of the wirings M0_2 is isolatedly provided in a cell area RMCa on one side of the tap area TAP_VB and a cell area RMCb on the other side of the tap area TAP_VB. Other configurations of the first modification may be the same as the corresponding configurations of the above-described embodiment. As described above, even though the wiring M0_2 is isolated, a problem does not occur because the wiring M0_2 is connected to the wiring M0_1 via the via contact V0 with low resistance. -
FIG. 16 is a plan view illustrating an example of a configuration of a semiconductor storage device according to a second modification. In the second modification, the via contact V0 is arranged in the X direction over the whole wiring M0_2. Accordingly, the resistance between the wiring M0_2 and the conductor slit LI_ST becomes further lower. Other configurations of the second modification may be the same as the corresponding configurations of the above-described embodiment. As described above, the via contact V0 may be arranged in the whole wiring M0_2. The size and the number of via contacts V0 may be set according to the current flowing through the via contacts V0. - While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the present disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the present disclosure.
Claims (16)
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